• Jarrod Mosier, Robert F Reardon, Paige A DeVries, Jamie L Stang, Ashley Nelsen, Matthew E Prekker, and Brian E Driver.
• Department of Emergency Medicine and Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep, University of Arizona College of Medicine, Tucson, Arizona.
• J Emerg Med. 2020 Nov 1; 59 (5): 637-642.

BackgroundIn patients requiring emergency rapid sequence intubation (RSI), 100% oxygen is often delivered for preoxygenation to replace alveolar nitrogen with oxygen. Sometimes, however, preoxygenation devices are prematurely removed from the patient prior to the onset of apnea, which can lead to rapid loss of preoxygenation.ObjectiveWe sought to determine the elapsed time, on average, between removing the oxygen source and the loss of preoxygenation among non-critically ill patients in the emergency department (ED).MethodsWe conducted a prospective, crossover study of non-critically ill patients in the ED. Each patient received two identical preoxygenation trials for 4 min using a non-rebreather mask with oxygen flow at flush rate and a nasal cannula with oxygen flow at 10 L/min. After each preoxygenation trial, patients underwent two trials in random order while continuing spontaneous breathing: 1) removal of both oxygen sources and 2) removal of non-rebreather mask with nasal cannula left in place. We defined loss of preoxygenation as an end-tidal oxygen (exhaled oxygen percentage; EtO2) value < 70%. We measured EtO2 breath by breath until loss of preoxygenation occurred.ResultsWe enrolled 42 patients, median age was 43 years (interquartile range [IQR] 30 to 54 years) and 72% were male. Median time to loss of preoxygenation was 20 s (IQR 17-25 s, 4.5 breaths) when all oxygen devices were removed, and 39 s (IQR 21-56 s, 8 breaths) when the nasal cannula was left in place.ConclusionsIn this population of non-critically ill ED patients, most had loss of preoxygenation after 5 breaths if all oxygen devices were removed, and after 8 breaths if a nasal cannula was left in place. These data suggest that during ED RSI, preoxygenation devices should be left in place until the patient is completely apneic.Copyright © 2020 Elsevier Inc. All rights reserved.

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